Dad's Stress Changes His Sperm: Brain Development of Future Children Affected

Is Dad stressed? It may not be a good thing for your future children. It turns out that sperm is affected by stress, whether experienced as a preadolescent or adult, and could give any sons or daughters a blunted reaction to stress--a response is associated with several mental disorders.

Stress felt by mothers during pregnancy has previously been shown to affect the neurodevelopment of offspring and even increase the risk for certain diseases. Yet a father's influence on his children is less clearly understood. In order to examine how men might be affecting their children, researchers looked at the effect of stress on preadolescent and adult male mice.

The male mice were exposed to six weeks of chronic stress before breeding either throughout puberty or only adulthood. In order to cause this stress, researchers employed a variety of techniques; these included moving the mice suddenly to another cage, placing predator odors near their cages (such as fox urine), creating strange noises or introducing a foreign object into a cage.

So how were the mice's children affected? It turns out that offspring from stressed mice fathers displayed significantly blunted levels of the stress hormone, corticosterone, in response to stress. In humans, this hormone is cortisol.

In order to understand how else these offspring were affected, the researchers also examined changes in gene expression in certain brain regions involved in stress regulation: the paraventricular nucleus (PVN) and the bed nucleus of stria terminals. The scientists found an increased expression of glucocorticoid-responsive genes in the PVN. This particular change supports a possible mechanism where increased negative feedback sensitivity may be explained.

The researchers didn't only find out the effects of dad's sperm on his offspring, though. They also found out what caused the changes in the first place. They looked at a series of microRNAs in the sperm that uniquely contribute to post-fertilization gene expression. They found that in the stressed dads, there was a significant increase in expression of nine microRNAs, which may be targeting the stores maternal messenger RNAs in the egg at fertilization.

Yet this response in offspring could actually provide an evolutionary advantage--depending on situation. It's possible that the reduced psychological stress response could ensure their survival in a more stressful environment.

Currently, the researchers are examining the mechanism by which the sperm microRNAS act at fertilization. They could be used as biomarkers in human diseases, which means that researchers could begin to predict who has been exposed to what. The findings also show that keeping dad cool and calm is better than letting him stress out.